What is the recommended management for a patient with an incidentally discovered meningioma, considering tumor size, growth, symptoms, and overall health?

Meningioma Management

For incidentally discovered meningiomas, asymptomatic lesions <30 mm should be observed with serial MRI surveillance every 6-12 months, while symptomatic meningiomas or those ≥30 mm require surgical resection if accessible, followed by radiation therapy for incomplete resection or higher-grade tumors. 1

Initial Diagnostic Workup

MRI with contrast is the mandatory imaging modality for all suspected meningiomas, providing detailed characterization with typical features including homogeneous dural-based enhancement, dural tail sign, and CSF cleft between tumor and brain. 1, 2 CT is significantly inferior and frequently misses small lesions, though it may identify calcifications present in up to 50% of cases. 1

Advanced Imaging Considerations

• Somatostatin receptor (SSTR) PET imaging should be obtained when tumor extension is unclear or to differentiate recurrence from post-treatment changes. 1, 2
• 3D isotropic T1-weighted gradient echo sequences with contrast provide optimal visualization for surgical planning. 1

Treatment Algorithm Based on Size and Symptoms

Asymptomatic Small Meningiomas (<30 mm)

Observation is the recommended approach with the following caveats: 1

• Serial MRI surveillance every 6-12 months 1, 2
• Surgery may be considered if the tumor is accessible and potential neurological consequences exist 1
• Elderly patients or those with significant comorbidities should be observed regardless of accessibility 1
• Tumors in eloquent, deep, or brainstem locations warrant observation due to higher surgical morbidity (5-18% for deep-seated lesions, nearly 50% early morbidity for brainstem locations) 1

Symptomatic Small Meningiomas (<30 mm)

Surgical resection is indicated if accessible, followed by: 1

• Radiation therapy if WHO grade 3 (malignant) 1
• Radiation therapy if incomplete resection occurs 1
• Observation with close surveillance if complete resection achieved for WHO grade 1 1

Large or Growing Meningiomas (≥30 mm)

Complete surgical resection with removal of dural attachment is the treatment of choice when feasible, achieving Simpson grade I resection in 83-100% of cases in experienced centers. 2 Modern image-guided surgery (frameless stereotaxy) improves precision and reduces surgical complications. 1, 2

Surgical Decision-Making Factors

Surgery should be pursued when: 1

• Neurological symptoms are present
• Evidence of growth on serial imaging
• Tumor is accessible with acceptable surgical risk
• Patient has reasonable life expectancy

Critical surgical consideration: Incomplete dural resection significantly increases recurrence risk; the dural attachment must be completely excised when feasible. 2 Even with complete resection of benign meningiomas, up to 20% recur within 25 years, necessitating lifelong follow-up. 1, 2

Radiation Therapy Indications

Post-Surgical Adjuvant Therapy

External beam radiation therapy (EBRT) is mandatory for: 1, 2

• WHO grade 3 (malignant) meningiomas after surgery
• Subtotally resected WHO grade 2 (atypical) meningiomas
• Incompletely resected benign meningiomas (improves progression-free survival from ~50% to >80%) 2

Primary Radiation Therapy

Stereotactic radiosurgery (SRS) is effective as monotherapy for: 2

• Residual or recurrent meningiomas <3 cm in diameter
• Tumors in eloquent areas with unacceptable surgical risk 1
• High-risk patients or elderly individuals who refuse surgery 3

Important caveat: Radiosurgery is not recommended for asymptomatic meningiomas that are surgically accessible. 1

Risk Stratification for Higher-Grade Pathology

Non-skull base location and male sex each confer 2-fold increased risk for WHO grade II/III pathology. 4 This has critical implications:

• 97% of operations are performed for tumor size and symptoms, not concerning features 4
• These higher-risk patients require more aggressive surveillance and lower threshold for intervention 4
• Prior surgery increases risk 3-fold for higher-grade pathology at recurrence 4

Post-Treatment Surveillance Protocol

MRI without and with contrast every 6-12 months is the standard surveillance approach for all meningiomas. 1, 2 The post-radiotherapy MRI should be considered the "new baseline" rather than the post-surgical MRI. 1

• After achieving stable disease (typically 5-10 years), follow-up intervals can be extended 5
• SSTR PET imaging is useful for distinguishing recurrence from post-treatment changes 1, 2

Common Pitfalls to Avoid

Not all enhancing dural-based lesions are meningiomas—brain metastases, gliomas, and primary CNS lymphoma can mimic meningiomas on imaging. 2 MRI findings that should alert to possible mimics include marked T2-hypo- or hyperintensity, absence of dural tail, and dural displacement sign. 1

Never rely on CT alone to exclude meningioma, as negative CT does not rule out diagnosis, particularly for smaller or non-calcified lesions. 1

Special Populations and Locations

Calcified Meningiomas

Surgical risks are substantially higher for deep-seated (5-18% morbidity), brainstem (nearly 50% early morbidity), and intraventricular locations (significant blood loss risk). 1 Observation is strongly preferred for asymptomatic calcified meningiomas in these locations, especially with advanced age or comorbidities. 1

Falcine Meningiomas

Complete surgical resection including dural attachment achieves Simpson grade I in 83-100% of cases. 2 For incompletely resected benign falcine meningiomas, adjuvant radiotherapy improves progression-free survival from approximately 50% to over 80%. 2